What’s that beneath the power-bulging aluminium bonnet of the new M3, a V8? BMW’s four-seat super-coupé is potentially now closer to the performance of supercars than ever, and far removed from the four-pot original. That’s progress. But then, it’s heavier too, for safety, comfort and technology’s sake – sufficiently so that even the former straight-six wasn’t powerful enough. Cue the new 4.0-litre masterpiece, built on the line that casts Nick Heidfeld’s F1 engine, swimming in ion flow technology, double VANOS valve timing and other 21st century features necessitating a 50-input ECU. Yet it’s 15kg lighter than the old six.

The M3 is “80% different” to a regular coupé. Only the doors, boot, glass and lights are the same, and there’s no mistaking the hunkered, wide-arched stance. It oozes muscle, buoyed by the lightweight carbon fibre roof. Is it the coolest feature of any new car this year? You won’t be confusing it with a 320d M Sport. As for the people it’s aimed at, BMW says that the M3’s skills and character are so similar to the Porsche 911, “they’re like relatives”. Only this is nearly £10k cheaper, and faster in base guise. Is it the best M BMW ever?

Performance

No two ways about it. The new V8 is glorious. The sound captivates first. Rich and layered, there’s character that the more Teutonic Audi RS4 lacks. Then you realise it’s responding to your right foot with nerve-like impulsiveness (that’s the eight individual throttle butterflies). You’re directly wired to it. Is it this encouraging you to exploit the 420 horses, or the huge reserves of torquey response from down at 2,000rpm? Either way, it’s ever-eager. And interestingly, I was intoxicated, travelling fast, yet barely breached 6,000rpm at first. I could still get the back out, still dispatch any other traffic I encountered.

The baritone turns operatic the first time you hit the 8,400rpm redline. It’s an ethereal experience. The endorphins are still flowing inside me. Staggeringly aurally intoxicating, the M3 is also ferociously fast here, battering you with speed, not just vocals (and quad exhausts treating pedestrians, too). Such is the blistering range, two gears of the manual shift are enough. Ah, but if only the electronics were so simple. Like the M5, there are menus, ‘M’ buttons, ‘Power’ buttons galore. Only here, power never alters, just the feel of its delivery. Even BMW admits owners will set and forget after three weeks.

Ride and handling

“The whole car should unify,” says Rolf Sheibner project manager for M cars. It certainly does. An hour in and I was caning the engine yet had barely considered the rest of it. The front, so agile and light, yet grippy, the assured fluidity through tricky sequences, the unflappable composure across beaten-up Spanish tarmac. Only after being taken for granted did these towering achievements dawn. It’s how the whole gels rather than individual facets that wows: the M3, not just its nose, darts into corners with weight-defying finesse. The M3, not just its rear, adopts gracefully controlled arcs (with stability disengaged) out of them.

Pity about the steering. Oh, it’s fast and direct off-centre, while on-track brutality is telegraphed confidently. But it’s hazy at centre and faster driving can see you ‘biting’ with the wheel, trying to summon some reassurance. This, on the awesome Ascari race track, was unnerving. Simply, it lacks a Porsche’s delicate detail, despite four bespoke Michelins with, between then, three separate compounds. Cunningly, the unflappable brakes turned out to have bespoke track pads, too. BMW didn’t tell us, so we puzzled at the squeaks and grumbles and can’t say what the regular stoppers are like. Such highs, then, but not a Porsche vanquishing.

Interior and safety

M, not BMW, are responsible for the interior. So you wonder how they missed the towering driver’s seat. At least it’s firmly supportive, with electrically-squeezing side bolsters and extending under-thigh support. Those in the rear get two commodious pews, too – whose backrest is constructed from glassfibre, weighing 35% less than standard (but costing “a few times more”, too). Other expensive details include the red-needled rev counter with its extending-when-warm redline, plus a spongy, thick steering wheel and trad stubby gearlever. Both, like the damping properties of the seat foam, were specified by chassis guys, not interior designers.

UK buyers get ample kit for their £50k: sat nav, Xenons, electric seats, climate, 18-inch alloys. 19”s are optional and, said the engineer, “for those seeing a more direct front end”. Yeah, and those seeking more bling. And here’s something significant. All the test cars were fitted with EDC electronic dampers, a £1,200 option and, reckoned the engineer, a must-have. The M3 has a wider repertoire with them, both for ride and handling. It won’t be the real deal without. Here’s hoping customers realise that. And safety? Airbags and stability control are complemented by those considerably raised dynamic limits. It’s faster, but more competent with it.

Economy

295g/km of CO2 and 22.8mpg won’t have bunny rabbits applauding the M3 from the hedgerows. You may scoff at BMW’s Efficient Dynamics talk here; there’s regenerative breaking, obsessive weight saving galore – goodness, even a shift-up blinker (for the planet, not the engine’s sake). Yet even BMW is twitchy about headline economy figures. You’ll still struggle to see 20mpg. Still, stats show it’s more powerful yet more economical than before (and less thirsty than all its rivals). Building it on the regular 3-Series production line saves construction consumption too. In supercar terms, it’s moderately green.

The MSN Cars verdict: 5/5

The M3 is a less aggressive but more well-rounded car before, with searing sophistication in places and the colossal performance courtesy of one of the best engines you can buy. Only the steering disappoints.